[Install] Improve installation script

Two changes:
  * get rid of complicated determining of latest setuptools
    package URL and switch to usage of script ez_setup.py
  * run script ez_setup.py in any case, no matter if we have
    setuptools version lesser that 0.8 or not. As result, we
    will always have latest setuptools version in virtualenv

These changes simplify the code a lot and provide reliable
installation of latest setuptools version.

See details about usage of script ez_setup.py
at https://pypi.python.org/pypi/setuptools

Change-Id: Ia8980ad4afc22daa25258c219861e5949930d199

install_rally.sh

@@ -273,30 +273,6 @@ download() {
     wget -nv $VERBOSE --no-check-certificate -O "$@";
 }
 
-download_setuptools () {
-    local url
-    # NOTE(stpierre): This (admittedly ugly) one-liner parses the JSON
-    # returned from pypi and fetches the URL for the latest version of
-    # the source (i.e., .tar.gz) package. It's safe here to look for
-    # the .tar.gz explicitly (rather than matching on package type ==
-    # source) because we untar it later anyway.
-    url=$(python -c '
-import json
-import urllib2
-
-print [u["url"]
-       for u in json.load(urllib2.urlopen("http://pypi.python.org/pypi/setuptools/json/"))["urls"]
-       if u["filename"].endswith(".tar.gz")].pop()')
-
-    if [ -n "$url" ]; then
-        download "$(basename "$url")" "$url"
-    else
-        die $EX_PROTOCOL "Setuptools not found on PyPI!" <<__EOF__
-Unable to download package 'setuptools' from PyPI.
-__EOF__
-    fi
-}
-
 install_required_sw () {
     # instead of guessing which distribution this is, we check for the
     # package manager name as it basically identifies the distro
@@ -446,30 +422,18 @@ __EOF__
     download "$VIRTUALENV_DST" "$VIRTUALENV_191_URL"
     "$PYTHON" "$VIRTUALENV_DST" $VERBOSE -p "$PYTHON" "$DESTDIR"
 
-    . "$DESTDIR"/bin/activate
+    cd "${DESTDIR}" && . bin/activate
 
-    # Recent versions of `pip` insist that setuptools>=0.8 is installed,
-    # because they try to use the "wheel" format for any kind of package.
-    # So we need to update setuptools, or `pip` will error out::
-    #
-    #     Wheel installs require setuptools >= 0.8 for dist-info support.
-    #
-    if pip wheel --help 1>/dev/null 2>/dev/null; then
-        (cd "$DESTDIR" && download_setuptools)
-        # setup.py must be called with `python', which will be the
-        # python executable inside the virtualenv, not `$PYTHON',
-        # which is the system python.
-        if ! (cd "$DESTDIR" && tar -xzf setuptools-*.tar.gz && \
-              cd setuptools-* && python setup.py install);
-        then
-            die $EX_SOFTWARE \
-                "Failed to install the latest version of Python 'setuptools'" <<__EOF__
+    # Setuptools>=0.8 is required to support "wheel" format, otherwise
+    # pip will fail with an error. To be sure, just run upgrade to the
+    # recent version of setuptools
+    download - https://bootstrap.pypa.io/ez_setup.py | python - --insecure\
+        || die ${EX_SOFTWARE}\
+            "Failed to install the latest version of Python 'setuptools'" <<__EOF__
 
 The required Python package setuptools could not be installed.
 
 __EOF__
-        fi
-    fi
 }
 
 setup_rally_configuration () {